Download Neuro Pathways

Neuro Pathways
Pain/temperature:
Body: Lissauer’s tract  substantia gelatinosa  contralateral spinothalamic tract 
VPL  posterior internal capsule  postcentral gyrus
Head: trigeminal n.  spinal trigeminal tract  spinal trigeminal nucleus 
contralateral spinothalamic tract  VPM  posterior internal capsule  postcentral
gyrus

Note: The homunculus of the facial tract has the midline structures in the superior
brainstem with lateral in the inferior brainstem; it also has the superior (V1)
structures in the anterior tract and the inferior (V3) in the posterior tract.
Touch/position:
Arm: fasciculus cuneatus  nucleus cuneatus  contralateral medial lemniscus  VPL
 posterior internal capsule  postcentral gyrus
Leg: fasciculus gracilis  nucleus gracilis  contralateral medial lemniscus  VPL 
posterior internal capsule  postcentral gyrus
Face: trigeminal n.  main sensory nucleus  contralateral medial lemniscus  VPL
 posterior internal capsule  postcentral gyrus
Visual:
retina  optic n.  optic chiasm  bilateral optic tract  LGN
 retrolenticular/sublenticular internal capsule  occipital lobe
 superior brachium  pretectal area  (posterior commisure)  EdingerWestphal nucleus  eye muscles
Oculomotor:
Saccades: frontal eye field  (superior colliculus)  contralateral PPRF 
abducens nucleus
 abducens n.  lateral rectus (ends contralaterally)
 contralateral MLF  oculomotor nucleus  oculomotor n.  medial
rectus (ends ipsilaterally)
Pursuit: frontal eye field and visual association cortex  pontine nucleus 
contralateral flocculus  vestibular nuclei  contralateral abducens nucleus
 abducens n.  lateral rectus (ends ipsilaterally)
 contralateral MLF  oculomotor nucleus  oculomotor n.  medial
rectus (ends contralaterally)
Olfactory:
olfactory n. bundles  olfactory bulb  uncus/amygdala
 Note: This pathway doesn’t relay in the thalamus or cross the midline
Gustatory:
taste buds  solitary tract  nucleus of the solitary tract  anterior insula
 Note: This pathway doesn’t relay in the thalamus or cross the midline
Vestibular:
vestibulocochlear n.  vestibular nuclei
 medial vestibulospinal tract (in MLF)  head posture
 lateral vestibulospinal tract (in MLF)  body posture
 oculomotor pathway
 inferior cerebellar peduncle  flocculonodular lobe
 thalamus  cortex (regions not specified)
Motor output:
precentral gyrus  posterior internal capsule  cerebral peduncle  basal pons 
pyramid  pyramidal decussation  contralateral corticospinal tract  lower motor
neuron  ventral root  output
Basal ganglia (speed of movement, involuntary and abnormal postures):
(Direct pathway):
cortex  (glutamate +)
compact substantia nigra  (dopamine, D1 receptors +)
 striatum (caudate, nucleus accumbens, putamen)  (GABA -)
 globus pallidus internal segment
(Indirect pathway):
compact substantia nigra  (dopamine, D2 receptors +)
globus pallidus external segment  (+)
 subthalamic nucleus  (+)
 globus pallidus internal segment
globus pallidus internal segment (also reticular substantia nigra) (GABA -)  ansa
lenticularis, lenticular fasciculus  VA/VL  (glutamate +)  posterior internal
capsule  precentral gyrus, premotor cortex (voluntary movement planning),
supplementary motor areas (complex, self-paced movements)
Cerebellum (uncoordinated ataxia, tremor, dysmetria):
Intermediate: cortex, periphery  interposed nuclei 
 superior cerebellar peduncle  red nucleus  spinal cord
 VA/VL  posterior internal capsule  precentral gyrus, premotor cortex,
supplementary motor areas
Lateral: cortex
 inferior olive  inferior cerebellar peduncle
 pons  middle cerebellar peduncle
 dentate nucleus
 red nucleus  inferior olive  inferior cerebellar peduncle
loop back to dentate nucleus
 superior cerebellar peduncle  VA/VL  posterior internal
capsule  precentral gyrus, premotor cortex, supplementary motor
areas
Vermis: spinocerebellar input  fastigial nucleus
 vestibular nuclei
 reticular formation
Hypothalamus:
Temperature: preoptic/anterior sensitive to high temperatures  cooling
posterior sensitive to low temperature  heating
Osmotic thirst: preoptic/anterior (OVLT)  anterior pituitary (supraoptic,
paraventricular)
Volumetric thirst: serum angiotensin  SFO
Eating: high fat, high glucose
 inhibit LH
 excite VMH (energy regulator)
 stop eating
low fat, low glucose
 excite LH
 inhibit VMH
 eat
Hippocampus:
Papez circuit: hippocampus
 fornix  mammilary bodies  mammilothalamic tract → anterior nucleus 
cingulate, parahippocampal gyri  loop back to hippocampus
 fornix → hypothalamus  prefrontal cortex  association cortex  loop
back to hippocampus
 amygdala  septal areas and loop back to hippocampus
Amygdala:
amygdala
 stria terminalis  hypothalamus, septal area
 amygdalofugal
 DM thalamus
 brainstem
 cingulate, parahippocampal gyri
Sleep:
rostral medulla/caudal pons reticular formation  inhibits ARAS  causes sleep
tubermammilary nucleus  (histamine)  REM sleep
 Note: the preoptic/anterior hypothalamus blocks histamine
Pain modulation:
pain afferent  periaqueductal grey  nucleus Raphe magnus  output
Micturition:
Storage: T11-L2  inhibit parasympathetic  detrusor relaxation
S2 (Onuf’s nucleus)  stimulates sphincter
Elimination: detrusor stretch  pontine micturition center
 S2-S4  stimulates parasympathetic  detrusor constriction
 inhibition of S2 (Onuf’s nucleus)  relaxes sphincter
Neuro Reflex Arcs
Stretch: afferent → dorsal root → spinal cord → ventral root → efferent
Flexor: stretch reflex ascending/descending to multiple levels
Near/light: light on retina → optic n. → optic chiasm → optic tract → LGN → superior
brachium  pretectal area  (posterior commisure)  Edinger-Westphal nucleus →
MLF → oculomotor n.
→ ciliary ganglion → short ciliary n. → ciliary contraction/papillary sphincter
contraction
→ medial recti muscle contraction
Dark: hypothalamus → intermediolateral cell column → superior cervical ganglion →
dilator contraction
Blink: cornea touch → spinal trigeminal nucleus → bilateral facial motor nuclei →
orbicularis oculi
Vestibuloocular: vestibular n. → vestibular nuclei → abducens nucleus → eye muscles
Vesicovesical: detrusor stretch → S2-S4 → parasympathetic stimulation → detrusor
contraction